Slurry explosives or blasting agents are used commonly in the mining industry. They generally contain a thickened oxidizer salt solution that forms a continuous aqueous phase throughout which is dispersed solid and/or liquid fuels, sensitizers, density reducing agents and other ingredients. Equipment for the bulk delivery of these blasting agents have been developed. For example, U.S. Pat. Nos. 3,303,738 and 3,380,333 disclose a method and apparatus for the bulk delivery of slurry blasting agents into a borehole. The disclosed apparatus is a heavy duty truck upon which is housed equipment for storage and transportation of blasting agent ingredients, for the blending and mixing of such ingredients into a slurry blasting agent and for the pumping of the blended slurry blasting agent into a borehole. Since the truck is self-contained with respect to the equipment for formulating and pumping the slurry blasting agent, it can be driven to the desired blasting site and there operated so as to manufacture and deliver the slurry blasting agent on-site and into a borehole. Thus, the slurry blasting agent ingredients, which are not detonable by themselves, can be transported safely by the truck, and a detonable blasting agent is formed only immediately prior to delivery of the agent into a borehole for subsequent detonation. The inherent safety advantages of this system are obvious.
Another advantage of this "site-mixed" "pump-truck" system is that the proportion of the ingredients being blended can be varied continuously or step-wise in a predetermined manner, and thus the composition of the slurry blasting agent can be tailored to meet varying blasting conditions, even within a single borehole. Other truck systems which simply repump or extrude slurry blasting agents previously formulated at a stationary facility do not have this advantage or the previously described safety advantage. The site-mixed system has received worldwide acceptance in many different types of mines and mining conditions. U.S. Pat. No. 4,112,240 also discloses a site-mixed system.
In contradistinction to slurry blasting agents, emulsion explosives or blasting agents have a continuous oil phase rather than a continuous aqueous phase. Droplets of an aqueous solution of oxidizer salt are dispersed or emulsified throughout the continuous oil phase and, as desired, solid ingredients such as undissolved oxidizer salt, fuel, or density reducing agents also are dispersed throughout the continuous oil phase. These blasting agents are referred to herein as water-in-oil emulsion blasting agents.
Water-in-oil emulsion blasting agents are known in the art. See, for example, U.S. Pat. Nos. 4,141,767; 4,110,134; 3,447,978 and 3,161,551. Water-in-oil emulsion blasting agents are found to have certain distinct advantages over conventional slurry blasting agents, as explained in U.S. Pat. No. 4,141,767. The above patents describe certain specialized methods for the manufacture of water-in-oil emulsion blasting agents, and a method and apparatus for the manufacture of such agents is described in U.S. Pat. Nos. 4,008,108 and 4,138,281. However, applicants are unaware of any site-mixed system for the delivery of water-in-oil emulsion blasting agents.
The present invention can be described as a site-mixed system for water-in-oil emulsion blasting agents which can be either cap sensitive or non-cap sensitive. This invention combines the above-described advantages of a site-mixed system and of water-in-oil emulsion blasting agents. Despite the advantages of combining a site-mixed system with a water-in-oil emulsion blasting agent, such combination has not been achieved heretofore.